Hypermiling: The Complete Guide to Saving Gas

Hypermiling

People seem to complain a lot about high gas prices, and rightfully so as the average American spends more than $2,000 on gasoline each year. That should mean the logical next step involves learning how to burn less fuel while driving, right? Strangely enough, that doesn’t seem to be the case. Most people must just like to complain, because they won’t change their terrible driving habits, or switch to a reasonable vehicle that doesn’t weigh 6,000 pounds.

If you’re one of the people cruising around town in one of those overpriced, oversized, oversold SUVs, please sell it and realize that you are the epitome of waste. You do not need a 350 horsepower engine and a few thousand pounds of steel to commute. You definitely don’t need it when the only thing that you haul is yourself and an occasional friend across town.

If you’re one of the few other Americans who despises inefficiency and waste, there is a growing population of “hypermilers” throughout the country who share ideas that encourage efficient driving habits. Hypermiling is the art of frugal, efficient driving, and it’s an absolute gem of a hobby.

I’ve been hypermiling for close to 6 years now, and I’m still improving my game. Like most frugal habits, this one requires careful thought and continuous reflection. The reward for the extra effort behind the wheel is a huge decrease in gasoline consumption and much better mileage on each tank of gas. I’m talking 25%+ better than the EPA estimate, and 50%+ better than most other drivers on the road.

EPA stands for Environmental Protection Agency. They rate the fuel efficiency of all cars on the road. Most people would love to simply get the EPA estimates, but most hypermilers laugh at those numbers and shoot for much, much better gas mileage.

For example, I currently drive an automatic 1996 Saturn SL1 with 120,000 miles. the EPA says that the car gets 23MPG-City, 33MPG-Highway. While hypermiling over the last 2 years, I’ve averaged 30-City, 40-Highway.

With the 1998 5-speed Saturn SL1 that I owned before my current car, I would average close to 40MPG-City and 43MPG-Highway. That’s crushing the EPA estimates.

If you’d like to see similar numbers, here is how to do so.

Plan trips and avoid idle time

Cars actually use roughly twice as much fuel when the engine is cold. And the engine is cold anytime it sits overnight, and twice as cold when it’s freezing outside. My small Saturn uses around 0.18 gallons of fuel per hour while idling when warm ($0.63/hour at $3.50 per gallon), and roughly twice that amount when cold. That’s low compared to other cars, and big V8 engines can use 4-5x that much fuel at idle.

As you can imagine, it is extremely inefficient to take short trips in cold weather, and you should always group errands together in one major outing. When running errands, go to your farthest destination first, and hit the others on the way back. This ensures that your vehicle is as warm as possible during multiple starts and stops.

Because engines burn so much more fuel at idle when cold, you should avoid letting your car “warm up” during cold weather. 1o-minute warm up sessions each morning can waste significant amounts of fuel, and it’s better to actually hop in and drive under minimal throttle to let it warm it up.

Outside of weather considerations, there are navigation issues to think about. Before ever driving, you should actually think about the route that you will be driving. You can take note while you drive, or go online and map it out. Check for stop signs, stop lights, high traffic roads, etc. Always plan the path of least resistance. Sometimes, highways or rural routes offer an advantage in transit time and gas mileage at the expense of a few extra miles on the odometer.

Perhaps most importantly, avoid unnecessary trips during peak traffic. The herd of crazed and overworked commuters are most difficult to deal with in large numbers, so it’s best to leave them alone during peak migration (rush hour). They won’t like anything about hypermiling, and will try everything to disrupt your astute, cash-saving driving habits. Running errands at off-peak times (such as 9-11am or after 8pm) can really improve gas mileage, decrease time wasted, and greatly improve overall mood.

Fix bad driving habits

Once you hop in and start driving, you must pay careful attention to your driving habits. After all, it’s not as if you get 25MPG all the time, that’s just a simple average. While accelerating from a stop, you are getting terrible gas mileage (often 10MPG or less), and while coasting without your foot on the gas, you’ll get more than 100MPG. Obviously, the goal here is to stop accelerating as much as possible.

Of course, the flip side of the equation involves less braking as well. Every time you use your brakes, you are killing the momentum that you just created by accelerating! So stop braking so much! When at all possible, don’t use the breaks. Pay attention to everything around you. Have your head on a swivel and always look ahead. Try to anticipate your next move, and try to time the next three stoplights.

Don’t run up on other drivers, and then throw on your breaks, then change lanes and accelerate again! Think ahead, look around, and switch lanes when you must. Pay attention to the color of stop-lights. I see people accelerating all the way up to stoplights that are clearly turning red. Why would you do that? It’s going to be red, and you’ll have to stop. Instead, just take your foot off the gas pedal and try to avoid stopping at the light altogether.

In summary, stop accelerating and braking all the time. Try not to use your brakes at all. That’s a fun game.

**Note that tome situations actually call for purposefully braking hard well before a stop light, to keep some momentum going.

For example: You’re doing well, coasting (not accelerating) up to that red light. If you slowly brake the whole time, you’ll quickly close the remaining road distance and be forced to a complete stop before the light changes to green. Well since that isn’t at all acceptable, stomp on the brakes early! When you brake hard initially, you can coast the remaining distance to the intersection at a slower speed. Perfect! With sound judgment and a little luck, you’ll arrive at a fresh green light and avoid a full stop, which will boost gas mileage considerably.

Pulse and Glide

When you have to speed up, the best way to accelerate is actually under high throttle at low RPMs. In other words, press the gas relatively hard (maybe 60%, not 100% throttle) in the highest gear possible, which keeps the RPMs low. This trick highlights one of the reasons that manual transmissions are vastly superior to automatics for hypermiling purposes – because you are always in control of the gearing.

Advanced hypermilers use this technique in something called the pulse and glide to set world records for driving efficiency. They shift into the highest gear possible, then swiftly accelerate to a modest speed. They then put the car in neutral or turn it off to coast back to the original speed. Then repeat. So on the highway, you could start at 45MPH in top gear, accelerate to 65MPH, coast back to 45MPH, and repeat.

It all might seem a little crazy and counter-intuitive, but it works because combustion engines are more efficient when working hard during short bursts than they are at working moderately hard in perpetuity. Take advantage of this by driving in the highest gear possible, which will keep RPMs low and gas mileage high.

This is all much harder to do in an automatic, and the best advice is probably to just keep RPMs as low as possible while driving. This can be exploited after you start understanding your car and the natural shift points. In our Saturn, which is a 4-speed automatic, I can increase throttle load and still keep it in a high gear at two distinct times. The first is when it shifts into third gear at roughly 31MPH, and the second when it shifts into fourth gear at roughly 44MPH. Right after the car shifts, the RPM load is quite low, and I can increase throttle without the car downshifting, which is an effective way to accelerate.

Coasting in neutral versus coasting in gear, and turning off the car

When doing the pulse and glide, or just coasting down a big hill, there is often a debate about whether to roll in neutral or in gear. When you shift to neutral, your car is just idling, which uses minimal fuel as I mentioned above ($0.63/hour for my tiny car). Obviously, that’s pretty insignificant, even if you have a gas guzzler.

However, most people don’t know that coasting in gear actually uses ZERO gas. Almost every car made since the 90s has a feature that shuts off the fuel supply when your foot is off the gas. This does come at a cost, which is the engine braking that accompanies being in gear. The car will automatically slow itself while in gear, so you have to weigh both options.

If you want to coast for a long period of time, and won’t be needing to brake, neutral is the better option even with the additional fuel cost. But if you are driving down a steep hill and don’t want a frictionless free-fall at full speed, leave it in gear to avoid using any gas, while enjoying a little bit of the engine braking that accompanies coasting in gear.

The other possibility when coasting is to simply turn off the engine when the car is in neutral. You should only do this if the coast will last longer than 12-15 seconds. If you need to use the gas before that, you are better off just idling. This is because restarting the car takes a small influx of gasoline, and causes minor stress on your car starter (which theoretically could die, but usually outlasts the car).

If you are going to be stopped for any amount of time, you should always shut off your engine. Don’t ever sit in parking lots with the car running. Don’t ever go through the drive through and sit idle for 5-10 minutes (just walk inside!). You should probably even shut off your car on the way to a long red stoplight. After all, there is nothing better than tricking the people stopped next to you into thinking that you have a hybrid!

Highway driving and the A/C fiasco

Engines are inefficient when running at 80MPH. Most cars reach peak fuel efficiency between 30-55MPH, and the sweet spot for many is right around 45MPH, right after they shift into the highest gear. If you keep top speeds between 75-80MPH on the highway, you’ll get 15-20% worse gas mileage than those who keep speeds of  60-65MPH. That’s neither good nor bad, it’s just more expensive. Is the extra speed worth the lost cash?

On long interstate trips, I’ll sometimes get behind a huge semi truck and draft. You need to maintain a few car lengths for this to be remotely safe, but you can see major improvement is gas mileage because of the reduced wind friction.

There is danger involved, but the reduction in drag, and therefore the increase in gas mileage, can be significant. A 2007 Myth Busters episode titled “Drafting for Money” produced the following findings:

Hypermiling drafting

In summary, drag is reduced 60% when following 10 feet behind a semi, and 21% even when seven car lengths behind. Fuel consumption is decreased nearly 40% at 10 feet, and still 11% even when trailing 100 feet behind. What distance do you feel justifies the increased risk?

Speaking of wind friction, did you know that it’s more expensive to leave the windows down than run the A/C on the highway? Somewhere between 45-50MPH is the tipping point between the two. Under 45MPH, windows down is cheaper. Above 50MPH, it’s cheaper to run the air.

If you’re considering running the A/C in city driving (low speed), you should know that doing so will often reduce gas mileage by 10%. There is a synergistic relationship between A/C usage and acceleration, meaning your gas mileage is absolutely terrible when doing both, and this will be most pronounced in cars like mine with very little horsepower to begin with. On cars with small engines, the A/C drag can be significant. To combat this problem, you can do a few things.  While decelerating, coasting or idling, turn the air on. While accelerating, turn the air off. Doing so will improve gas mileage.

Car modifications

A lighter vehicle is easier to move. Less weight requires less fuel to accelerate, and all else equal, a lighter vehicle will get better gas mileage. To begin, remove all accessory items from your car before driving.  Detach any outside accessories that add weight and reduce aerodynamics. Remove any dead weight and luggage that isn’t needed inside the car as well. For trips around town, think about ditching the spare tire and jack which weigh 50+ pounds.

In addition to reducing the weight, you can also reduce rolling resistance. Higher tire pressure means less contact with the road, and less rolling resistance while driving. In other words, highly inflated tires reduce friction between rubber and road, improving gas mileage. The only downside to fully inflated tires is a slightly rougher ride quality.

When inflating, don’t use the automobile manufacture recommendations, which are often around 30 PSI. Instead, inflate your tires to the tire’s maximum recommended PSI which is listed on the sidewall of the tire. I tend to inflate to the tire maximum without going over, but many people find that 1-3PSI of over-inflation will improve mileage further, without posing any safety issues.

How much will it improve mileage? Great question. Episode 153 of Myth Busters found that over inflating the tires (60 psi vs. 35 psi, which was the manufacturer’s recommendation) reduced the fuel consumption of their regular sedan by about 7.6%. They also tested slightly over-inflated tires (40 psi) with the same car, which resulted in a 6.2% decrease in fuel consumption. 6.2% is a lot!

Rolling resistance and vehicle weight are the low hanging hypermiling fruit. You can do much more, but it requires more work and/or risk. Many people fill cracks and open spaces on/under the car to further increase the aerodynamics and decrease drag. You can also partially block the front intake opening on the car, which will make the engine run slightly hotter and actually improve efficiency.

Consider other transportation

If you embrace the ideas in this article, you’ll see a huge improvement in gas mileage. However, what the heck does it even matter if your car gets 10 MPG to begin with? I mean honestly, why do so many Americans feel the need to drive a huge, inefficient vehicle around town? It doesn’t make any logical sense.

Unless you have to haul 5 kids around town, or need a work truck, you really should be driving a compact car equipped with a 4-cylinder engine (and preferably a manual transmission). That car should get at least 35MPG on the highway. There are tons of used cars that fit my criteria, and most can be purchased for less than $8,000 in excellent condition.

In addition to finding a reasonable vehicle, how about just driving less altogether? I ride the bus everyday for free because my employer (local university) pays for unlimited use. The university actually includes unlimited bus usage in the tuition cost for students, but still it’s empty almost every day. Instead of riding the free bus, students pay for parking permits and choose to drive! Are you kidding?

The best option is living close to work, and walking or riding a bicycle each day. Get your exercise while commuting for free. Now that’s a win, win.

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